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Formula: Mn2+6V5+Si5O18(OH)
Sorosilicate (Si2O7 groups), manganese and
vanadium- bearing mineral
Specific gravity: 3.65 to 3.75 measured, 3.727 calculated
Streak: Yellow-white
Colour: Brownish red
Solubility: Insoluble in water, hydrochloric and nitric acids
Common impurities: Fe,H2O
Environments
Medaite is formed at low temperatures in veinlets cutting manganese ores
(HOM).
Localities
At the type locality, the Molinello mine, Ne, Genoa, Liguria, Italy, medaite occurs as a rare associate of
tiragalloite in the abandoned
manganese mine. It appears as small brown grains embedded in brownish veinlets, a
few millimeters thick, cutting a black manganese ore made up mainly of
quartz and braunite, with traces of
serpentine. In these veins, which have almost no cavities, medaite never
occurs as euhedral crystals. The grains, measuring up to 1.5 mm in length but usually much smaller (0.2 to 0.4 mm) are either
isolated, surrounded nearly invariably by quartz, or grouped together into aggregates
measuring up to 10 mm in diameter
(AM 67.85).
Associated minerals include manganese-bearing
calcite, parsettensite and
albite, as well as tiragalloite,
braunite and quartz
(HOM).
At Fianel, Ausserferrera, Ferrera, Viamala Region, Grisons, Switzerland, medaite is associated with
palenzonaite, saneroite,
pyrobelonite, fianelite,
parsettensite, rhodochrosite,
kutnohorite, aegirine and
quartz
(HOM).
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